Almost half of the world’s most threatened sea turtle populations are found in the northern Indian Ocean, according to a new study carried out by the world’s top sea turtle experts.

Scientists have evaluated the state of individual populations of sea turtles, enabling them to determine the 11 most threatened, as well as the 12 healthiest.

The loggerhead turtle is one of the most widespread of all marine turtles and also the most highly migratory. Several of the most threatened sea turtle populations included loggerhead turtles.

Populations at risk

The results of the study have revealed that five of the world’s eleven most threatened populations of sea turtles are found in the northern Indian Ocean, with populations of loggerhead turtles and olive ridley turtles appearing particularly at risk.

Several threatened populations of both species occur in waters and on nesting beaches around countries such as India, Sri Lanka and Bangladesh.

“The report confirms that India is a home to many of the most threatened sea turtles in the world,” said Dr B.C. Choudhury, head of the Department of Endangered Species Management at the Wildlife Institute of India and a contributor to the study. “This paper is a wake-up call for the authorities to do more to protect India’s sea turtles and their habitats to ensure that they survive.”

The east Pacific Ocean from the USA to South America, and the east Atlantic Ocean off the coast of western Africa, have also been identified as areas with some of the world’s most threatened sea turtle populations.

The smallest of the marine turtles, the olive ridley turtle was identified as having a number of threatened populations in the northern Indian Ocean.

Highlighting healthy populations

The study also highlighted large sea turtle populations that are currently facing relatively low threat levels, with 12 populations identified as the healthiest in the world.

Among these healthy populations, which belong to five species including the hawksbill turtle and the green turtle, are populations with nesting and feeding areas in Australia, Mexico and Brazil.

It is the first comprehensive status assessment of all global sea turtle populations, and has been designed to provide a blueprint for future sea turtle conservation and research.

According to Roderic Mast, Co-Chair of the MTSG, CI Vice President, and one of the paper’s authors, “This assessment system provides a baseline status for all sea turtles from which we can gauge our progress on recovering these threatened populations in the future.”

“Through this process, we have learned a lot about what is working and what isn’t in sea turtle conservation, so now we look forward to turning the lessons learned into sound conservation strategies for sea turtles and their habitats.”

Identifying threats and priorities

As well as identifying the world’s most threatened sea turtle populations, the study looked at which threats had the most significant impact on these endangered turtles.

The study revealed that the most serious problems to sea turtles are being caused by fisheries bycatch (accidental catches of sea turtles by fishermen targeting other species) and the direct harvest of turtles or their eggs for food or turtle shell for commercial use.

A young hawksbill turtle caught in a fishing net. Although this species was identified as having some of the healthiest populations, it is not exempt from the many threats faced by sea turtles worldwide.

Dr Bryan Wallace, Director of Science for the Marine Flagship Species Program at CI, and lead author of the paper, said, “Before we conducted this study, the best we could say about sea turtles was that six of the seven sea turtle species are threatened with extinction globally.”

“But this wasn’t very helpful for conservation because it didn’t help us set priorities for different populations in different regions. Sea turtles everywhere are conservation-dependent, but this framework will help us effectively target our conservation efforts around the world.”

A paper on the study, entitled ‘Global Conservation Priorities for Marine Turtles’, has been published in the online science journal PLoS ONE.